众所周知，使用多进程的服务端模型有利于程序的健壮性。传统的做法是主进程负责收发数据，然后传给子进程来处理。这种做法的缺陷是需要大量的父子进程IPC，对效率来说是一种损失。
这里，我提出另外一种比较独特的做法，就是多个进程share socket，每次进程都可以accept，然后来自己处理。
几个关键点:
1) CreateProcess使用InheritHandle标记来share socket handle
2) 通过command line直接向子进程来传递父socket的值
3）使用Global Mutext来实现子进程互斥的accept
可以改进的地方
1) 使用动态进程池来程序具有更大的伸缩性
2）监控子进程的状态，处理僵死进程
下面是一个echo server 的例子来展示这项技术, FYI
父进程(SSParent.cpp)
#include <stdio.h>
#include <winsock2.h>
#include <windows.h>
#include <process.h>
#define MUTEX_NAME "sschild"
int main(int argc, char* argv[])
{
{ //init
WORD wVersionRequested;
WSADATA wsaData;
wVersionRequested = MAKEWORD( 2, 2 );
WSAStartup( wVersionRequested, &wsaData );
}
SOCKET s = socket(AF_INET,SOCK_STREAM,0);
if(s==INVALID_SOCKET)
{
printf("create socket failed!\n");
return -1;
}
{ //bind&listen
sockaddr_in sa;
sa.sin_family = AF_INET;
sa.sin_port = htons( 1500 );
sa.sin_addr.s_addr = 0 ;
int rc = bind(s,(sockaddr *)&sa,sizeof(sa));
if(rc == SOCKET_ERROR)
{
printf("bind failed:%d\n",::WSAGetLastError());
return -1;
}
listen(s,SOMAXCONN);
}
HANDLE hSocketMutex;
{ //create mutex
hSocketMutex = ::CreateMutex(NULL,FALSE,MUTEX_NAME);
if(hSocketMutex==NULL)
{
printf("fail CreateMutex:%d\n",::GetLastError());
return -1;
}
}
const int CHILD_NUMBER = 5;
HANDLE hProcess[CHILD_NUMBER];
{ //create child process
STARTUPINFO si = { sizeof(si) };
PROCESS_INFORMATION piProcess[CHILD_NUMBER];
char pCmdLine[256];
sprintf(pCmdLine,"SSChild %d",s);
for(int i=0;i<CHILD_NUMBER;++i)
{
if(!CreateProcess(NULL,pCmdLine,NULL,NULL,TRUE,0, NULL, NULL, &si, &piProcess[i]))
{
printf("fail CreateProcess:%d\n",::GetLastError());
return -1;
}
hProcess[i] = piProcess[i].hProcess;
CloseHandle(piProcess[i].hThread);
}
}
::WaitForMultipleObjects(CHILD_NUMBER,hProcess,TRUE,INFINITE);
{//close all child handle
for(int i=0;i<CHILD_NUMBER;++i)
{
CloseHandle(hProcess[i]);
}
}
//clean
CloseHandle(hSocketMutex);
closesocket(s);
WSACleanup( );
return 0;
}
子进程(SSChild.cpp)
#include <stdio.h>
#include <winsock2.h>
#include <windows.h>
#include <process.h>
#define MUTEX_NAME "sschild"
int main(int argc, char* argv[])
{
printf("sschild startup!\n");
{ //init
WORD wVersionRequested;
WSADATA wsaData;
wVersionRequested = MAKEWORD( 2, 2 );
WSAStartup( wVersionRequested, &wsaData );
}
DWORD pid = ::GetCurrentProcessId();
HANDLE hSocketMutex;
{ //open mutex
hSocketMutex = ::OpenMutex(MUTEX_ALL_ACCESS,FALSE,MUTEX_NAME);
if(hSocketMutex==NULL)
{
printf("fail OpenMutex:%d\n",::GetLastError());
return -1;
}
}
SOCKET s;
{ //get socket handle from cmdline
if(argc<=1)
{
printf("usage: sschild socket_handle\n");
return -1;
}
s = (SOCKET) atoi(argv[1]);
}
while(1)
{
WaitForSingleObject(hSocketMutex,INFINITE);
sockaddr_in sa;
int add_len = sizeof(sa);
SOCKET c = accept(s,(sockaddr*)&sa,&add_len);
ReleaseMutex(hSocketMutex);
if(c!=INVALID_SOCKET)
{
printf("[%d],client:%s port:%d connected!\n",pid,inet_ntoa(sa.sin_addr),sa.sin_port);
while(1)
{
char buffer[256]={0};
int rc= recv(c,buffer,255,0);
if(rc>0)
{
printf("[%d]recv msg:%s\n",pid,buffer);
send(c,buffer,strlen(buffer)+1,0);
}
else if(rc == SOCKET_ERROR)
{
printf("[%d]recv msg failed:%d\n",pid,::WSAGetLastError());
closesocket(c);
break;
}
else
{
printf("[%d]connection close\n",pid);
closesocket(c);
break;
}
}
}
else
{
printf("[%d]fail accept:%d\n",pid,::WSAGetLastError());
}
}
CloseHandle(hSocketMutex);
return 0;
}